And now that I look at it, V.hb does have a good point, in that some dogs are more naturally aggressive, and while I correct myself that not all vicious dogs are the result of their upbringing, I still stand to the fact that it is our responsibility to do everything in our power to correct the issue. Be it behaviour classes, corrective punishment or what not, we must ensure that our pets do not pose a threat to others. There are cases where the problem cannot be resolved, at which point it is our responsibility to ensure your dog is not a threat to others (ie. using a muzzle when outdoors, always having it on a leash, making sure he does not escape your premises, etc.)